Scanning probe microscope

Abstract

To provide a scan-type probe microscope which can easily determine a measurement position even when the numerical aperture of an objective lens is relatively large.SOLUTION: A scan-type probe microscope includes: a probe for scanning a sample; a light source for applying excitation light on the probe through an objective lens; and a detector for detecting fluorescence generated from the probe. The scan-type probe microscope further includes: a reflective member arranged between the objective lens and the sample; and an imaging device for taking an image of a reflection surface of the reflection member.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a scanning probe microscope.

Background Art

[0002] A scanning probe microscope is a device that images the shape and physical property values of a sample by scanning the sample with a minute needle-shaped probe.

[0003] Patent Document 1 discloses a scanning probe microscope that uses diamond having nitrogen-vacancy pairs (hereinafter referred to as NV diamond) as a probe, irradiates the probe with excitation light and microwaves, and collects fluorescence emitted from the nitrogen-vacancy pairs.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, no consideration is given to easily determining the measurement location from within the sample. In many scanning probe microscopes, an objective lens having a relatively large numerical aperture is used, so the field of view obtained through the objective lens is narrow, and it takes time and effort to determine the measurement location.

[0006] Therefore, an object of the present invention is to provide a scanning probe microscope capable of easily determining a measurement location even when the numerical aperture of the objective lens is relatively large.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides a scanning probe microscope comprising a probe for scanning a sample, a light source for irradiating the probe with excitation light via an objective lens, and a detector for detecting fluorescence generated by the probe, further comprising a reflective member disposed between the objective lens and the sample, and a reflective surface imaging device for imaging the reflective surface of the reflective member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a scanning probe microscope that can easily determine the measurement location even when the numerical aperture of the objective lens is relatively large. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the overall configuration of a scanning probe microscope. [Figure 2] This is a perspective view showing an example of the arrangement of a reflective element, a reflective surface imaging device, a probe, and a microwave antenna. [Figure 3] This figure shows an example of the arrangement of the probe and microwave antenna. [Figure 4] This figure shows an example of the position adjustment procedure. [Figure 5A] This is a top view showing an example of the sample structure. [Figure 5B] This is a cross-sectional view showing an example of the sample's structure. [Figure 6A] This figure shows an example of an image of a reflective surface taken at low magnification. [Figure 6B] This figure shows an example of an image of a reflective surface taken at high magnification. [Figure 7A] This figure shows an example of an image taken of a sample from the side at low magnification. [Figure 7B] This figure shows an example of an image taken of a sample from the side at high magnification. [Figure 8A] This figure shows an example of the structure of a reflective material. [Figure 8B] This figure shows an example of the structure of a reflective material. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of a scanning probe microscope according to the present invention will be described with reference to the accompanying drawings. In the following description and the accompanying drawings, components having the same functional configuration will be denoted by the same reference numerals, and redundant description will be omitted.

Embodiment

[0011] FIG. 1 is a diagram showing the overall configuration of a scanning probe microscope. In FIG. 1, the horizontal direction is the x-axis, the direction perpendicular to the paper surface is the y-axis, and the vertical direction is the z-axis. The scanning probe microscope includes a sample stage 7, a probe 3, a light source 14, an objective lens 9, a detector 15, a microwave antenna 6, a reflecting member 23, a reflection surface imaging device 34, and a computer 21. Hereinafter, each part will be described.

[0012] The sample stage 7 is a device that holds the sample 1 and controls the position of the sample 1 in the xyz directions, and is, for example, composed of a piezo stage. The sample stage 7 is disposed on an anti-vibration table 8.

[0013] The probe 3 is a minute needle that scans the sample 1 as the sample stage 7 moves in the xyz directions. The probe 3 has an NV diamond or silicon carbide or the like that includes an NV center 4 which is a light emission point. The probe 3 may be fixed to the tip of a probe driving unit 2 and its position may be controlled by the probe driving unit 2.

[0014] The light source 14 is a device that irradiates the probe 3 with excitation light 18. The excitation light 18 is, for example, laser light having a wavelength of 532 nm. The timing of irradiating the excitation light 18 may be controlled by the operation of an optical switch 13.

[0015] The objective lens 9 is a lens that focuses the excitation light 18 on the NV center 4 included in the probe 3. The excitation light 18 is irradiated on the NV center 4 along the optical axis of the objective lens 9. The position of the objective lens 9 may be controlled by an objective lens driving unit 10 composed of, for example, a piezo stage.

[0016] Detector 15 is a device that detects fluorescence 19 generated at the NV center 4 of probe 3. The fluorescence 19 generated at the NV center 4 reaches detector 15 via the objective lens 9, wavelength selection mirror 17, wavelength selection filter 16, lens 22, and pinhole 33. By passing through the wavelength selection mirror 17 and the wavelength selection filter 16, only fluorescence 19 of, for example, about 600 nm or more reaches detector 15. Also, the emission region of the NV center 4 is limited to 1 μm or less in the z direction by a confocal optical system composed of a pinhole 33 with a diameter of about several tens of μm and the lens 22 arranged before and after it.

[0017] The microwave antenna 6 irradiates the probe 3 with microwaves and is arranged at a predetermined distance, for example, within 50 μm from the probe 3. By detecting the fluorescence 19 while changing the wavelength of the microwaves irradiated to the probe 3, an optically detected magnetic resonance (ODMR) spectrum corresponding to, for example, Zeeman splitting that is the basis of magnetic field measurement can be obtained. The microwave antenna 6 may be fixed to the tip of the antenna drive unit 5 and its position may be controlled by the antenna drive unit 5.

[0018] The reflecting member 23 has a reflecting surface 23A that reflects the upper surface of the sample 1 and is arranged between the objective lens 9 and the sample 1. The reflecting member 23 is configured to be accommodated within the working distance (W.D.) of the objective lens 9. For example, when the W.D. is 4.5 mm, the tip of a glass tube with a diameter of 2 mm is cut at 45° with respect to the central axis of the glass tube, and a metal film is formed on the cut surface, thereby forming a reflecting member 23 with the metal film as the reflecting surface 23A. Note that the angle between the cut surface and the central axis is not limited to 45°. Also, the position and orientation of the reflecting member 23 may be controlled by the reflecting member drive unit 24.

[0019] The reflective surface imaging device 34 is a device for imaging the reflective surface 23A of the reflective member 23. The image of the upper surface of the sample 1 reflected on the reflective surface 23A of the reflective member 23 is not obtained through the objective lens 9, and therefore has a relatively wide field of view, for example, a field of view of about 2 mm square. Therefore, by using the image of the reflective surface 23A, the measurement location within the sample 1 can be easily determined.

[0020] Furthermore, the position and orientation of the reflective surface imaging device 34 may be controlled by the imaging device drive unit 25. For example, by moving the reflective surface imaging device 34, which is located to the side of the reflective member 23, in the z direction using the imaging device drive unit 25 to position it to the side of the sample 1, an image of the sample 1 taken from the x direction can be obtained. The image of the sample 1 taken from the side also has a relatively wide field of view because it is not taken through the objective lens 9.

[0021] Computer 21 is a device that controls the operation of each part according to a program, and also generates and displays various images.

[0022] The scanning probe microscope may also include a flip mirror 12 for separating reflected light from the sample 1 and an imaging device 20 for imaging the separated reflected light. The field of view of the image obtained by the imaging device 20 is relatively narrow because it is mediated through the objective lens 9, for example, about 200 μm square.

[0023] Using Figure 2, an example of the arrangement of the reflective member 23, the reflective surface imaging device 34, the probe 3, and the microwave antenna 6 will be explained. The arrangement of the reflective member 23, the reflective surface imaging device 34, the probe 3, and the microwave antenna 6 is not limited to the arrangement where all four are aligned on the same plane, as illustrated in Figure 1. Figure 2 illustrates an arrangement in which plane A, which includes the central axis of the reflective member 23 and the central axis of the reflective surface imaging device 34, intersects with plane B, which includes the central axis of the probe 3 and the central axis of the microwave antenna 6. The intersection angle between plane A and plane B is preferably close to 90°, and 90° is the best. In other words, the closer the intersection angle is to 90°, the larger the reflective member 23 can be made without interference between the pair of reflective member 23 and reflective surface imaging device 34 and the pair of probe 3 and microwave antenna 6, and the measurement location in the sample 1 can be determined with a wider field of view.

[0024] Furthermore, it is preferable that at least one of surface A and surface B includes the optical axis of the objective lens 9. Including the optical axis in either surface A or surface B allows for more precise adjustment of the measurement location. When both surface A and surface B include the optical axis, the intersection of surface A and surface B coincides with the optical axis.

[0025] An example of the arrangement of the probe 3 and microwave antenna 6 will be explained using Figure 3. The arrangement of the probe 3 and microwave antenna 6 is not limited to the arrangement in which they face each other across the optical axis of the objective lens 9, as exemplified in Figures 1 and 2. Figure 3 illustrates an arrangement in which the probe 3 and microwave antenna 6 are aligned in the z direction. In Figure 3, the probe 3 and microwave antenna 6 are connected to the probe drive unit 2 and the antenna drive unit 5, respectively, via a support member 36. The probe drive unit 2 and the antenna drive unit 5 are stacked on a base plate 35 that moves in the x and y directions on the optical base plate 32. With this structure, the sample 1 can be replaced without readjusting the positions of the probe 3 and microwave antenna 6. That is, the probe 3 and microwave antenna 6, whose positions have been adjusted by the probe drive unit 2 and the antenna drive unit 5, are adjusted relative to the sample 1 by the movement of the base plate 35.

[0026] Using Figure 4, we will explain step-by-step an example of the procedure for adjusting the positions of probe 3, microwave antenna 6, and sample 1 in the scanning probe microscope shown in Figure 1.

[0027] (S401) The position of probe 3 is adjusted. For example, based on the fluorescence 19 detected by the detector 15, the probe drive unit 2 is controlled by the computer 21 so that probe 3 is positioned within a predetermined distance from the optical axis of the objective lens 9. When the detector 15 detects fluorescence 19, the reflector 23 is retracted by the reflector drive unit 24 so that it does not overlap with the optical axis of the objective lens 9.

[0028] (S402) The position of the microwave antenna 6 is adjusted. For example, based on an image obtained by the reflective surface imaging device 34, the antenna drive unit 5 is controlled by the computer 21 so that the microwave antenna 6 is positioned within a predetermined distance from the probe 3. In S402, the reflective member drive unit 24 inserts the reflective member 23 between the sample 1 and the objective lens 9.

[0029] (S403) The position of sample 1 is roughly adjusted as illustrated in Figures 5A and 5B. Figure 5A is a top view of sample 1 having the sample pattern 27, and Figure 5B is a cross-sectional view of sample 1.

[0030] More specifically, the sample stage 7 is controlled by the computer 21 so that the measurement location of the sample 1 is positioned within the field of view, based on the captured images 28 shown in Figures 6A and 6B obtained by the reflective surface imaging device 34. When imaging is performed by the reflective surface imaging device 34, the reflective member 23 is inserted between the sample 1 and the objective lens 9 by the reflective member drive unit 24. Figure 6A is an image of the reflective surface 23A of the reflective member 23 taken at low magnification, and includes the reflective surface region 29 where the reflective surface 23A with a diameter of approximately 2 mm is visible, and the region other than the reflective surface region 29. The captured image 28 in Figure 6A, which was taken at low magnification, shows the sample 1, microwave antenna 6, probe 3, and the power supply pad 30 and power supply line 31 arranged around the sample 1. The power supply pad 30 and power supply line 31 supply current to the sample 1 and are used when observing the sample 1 which operates by the supply of current. Figure 6B is a high-magnification image of the reflective surface 23A of the reflective member 23, and is an enlarged image of the central part of Figure 6A. By using an image with a relatively wide field of view, such as the image 28 in Figure 6A, the time and effort required to determine the measurement location can be reduced. Furthermore, by using an image with a relatively high magnification, such as the image 28 in Figure 6B, the position of the sample 1 can be adjusted with high precision.

[0031] In addition to the captured images 28 in Figures 6A and 6B, the captured images 28 exemplified in Figures 7A and 7B may also be used for adjusting the position of the sample 1. The captured image 28 in Figure 7A is an image of the sample 1 taken from the side without using the reflective member 23, and is taken after moving the reflective surface imaging device 34 parallel to the optical axis of the objective lens 9. The captured image 28 in Figure 7B is an image taken at a higher magnification than Figure 7A. By using the captured images 28 in Figures 7A and 7B, the distance between the probe 3 and microwave antenna 6 and the sample 1 can be adjusted.

[0032] (S404) Fine-tuning of the position of sample 1 is performed. For example, based on a high-magnification, high-resolution image obtained by the imaging device 20, the sample stage 7 is controlled by the computer 21 so that the measurement point is positioned in the center of the field of view. When the imaging device 20 obtains an image, the reflective member 23 is retracted by the reflective member drive unit 24 so that it does not overlap with the optical axis of the objective lens 9. The fine-tuning in S404 may also be performed based on an image obtained by the reflective surface imaging device 34.

[0033] The positional adjustment of the probe 3, microwave antenna 6, and sample 1 is completed by the procedure described using Figure 4. In particular, in S403, the image of the reflective surface of the reflective member 23 is used by the reflective surface imaging device 34, making it easy to determine an appropriate measurement location within the sample 1. [Examples]

[0034] In Example 1, a reflective member 23 having a reflective surface 23A formed on the cut surface after cutting the tip of a glass tube at a 45° inclination angle was described. In Example 2, a reflective member 23 having a through hole 26 along with the reflective surface 23A will be described. Note that the configuration other than the reflective member 23 is the same as in Example 1, so the description will be omitted. An example of a reflective member 23 having a through hole 26 will be described using Figure 8A. Similar to Embodiment 1, the reflective member 23 shown in Figure 8A has a reflective surface 23A formed on a cross-section with a 45° inclination angle, and a through hole 26 through which the optical axis of the objective lens 9 passes is provided in the center of the reflective surface 23A.

[0035] Another example of a reflective member 23 having a through hole 26 will be described using Figure 8B. In the reflective member 23 illustrated in Figure 8B, a reflective surface 23A is formed on the side surface of a triangular prism, and a through hole 26 is provided in the center of the reflective surface 23A. The through hole 26 in Figure 8B is also provided so that the optical axis of the objective lens 9 passes through it.

[0036] By providing through holes 26 as shown in Figures 8A and 8B, detection by the detector 15 and imaging by the imaging device 20 become possible in S401 and S404 of Figure 4 without having to retract the reflective member 23. As a result, the effort required to adjust the positions of the probe 3, microwave antenna 6, and sample 1 is reduced.

[0037] The embodiments of the present invention have been described above. The present invention is not limited to the embodiments described above, and the components can be modified and implemented without departing from the spirit of the invention. Furthermore, the multiple components disclosed in the above embodiments may be combined as appropriate. In addition, some components may be deleted from all the components shown in the above embodiments. [Explanation of Symbols]

[0038] 1: Sample, 2: Probe drive unit, 3: Probe, 4: NV center, 5: Antenna drive unit, 6: Microwave antenna, 7: Sample stage, 8: Vibration isolation table, 9: Objective lens, 10: Objective lens drive unit, 12: Flip mirror, 10: Objective lens drive unit, 12: Flip mirror, 13: Optical switch, 14: Light source, 15: Detector, 16: Wavelength selection filter, 17: Wavelength selection mirror, 18: Excitation light, 19: Fluorescence, 20: Imaging device, 21: Computer, 22: Lens, 23: Reflective material, 23A: Reflective surface, 24: Reflective material drive unit, 25: Imaging device drive unit, 26: Through hole, 27: Sample pattern, 28: Acquired image, 29: Reflective surface area, 30: Power supply pad, 31: Power supply line, 32: Optical base plate, 33: Pinhole, 34: Reflective surface imaging device, 35: Base plate, 36: Support member

Claims

1. A probe for scanning the sample, A light source that irradiates the probe with excitation light through an objective lens, A scanning probe microscope comprising a detector for detecting fluorescence generated by the probe, A reflective member is disposed between the objective lens and the sample, A scanning probe microscope further comprising a reflective surface imaging device for imaging the reflective surface of the reflective member.

2. A scanning probe microscope according to claim 1, The scanning probe microscope is characterized in that the reflective member has a through hole through which the optical axis of the objective lens passes.

3. A scanning probe microscope according to claim 1, A scanning probe microscope further comprising an imaging device drive unit that moves the reflective surface imaging device parallel to the optical axis of the objective lens.

4. A scanning probe microscope according to claim 1, A microwave antenna that irradiates the probe with microwaves, An antenna drive unit that controls the position of the microwave antenna, A scanning probe microscope further comprising a probe drive unit for controlling the position of the probe.

5. A scanning probe microscope according to claim 1, The scanning probe microscope is characterized in that the probe has a diamond or silicon carbide having nitrogen-vacancy pairs.

Images